Island



(No Model.)

s. FENNER & J; 0. TAFT. MANUFACTURE OF TWIST DRILLS.

No. 437,187. PatentedSept. so, 1890.

W! INEEEEE: INVENTEIH UNITED STATES SULLIVAN FENNER AND JEROME O. TAFT,OF PROVIDENCE, RHODE ISLAND,

P TENT OFFI E; f

ASSIGNORS, BY DIRECT AND MESNE ASSIGNMENTS, TO THE 'UNITED' STATES TWISTDRILL COMPANY, OF SAME PLACE.

MANUFACTURE OF TWIST-DRILLS.

SPECIFICATION forming part of Letters Patent No. 437,187, datedSeptember 30,1890.

Application filed June 18, 1888.

To all whom it may concern.-

Be it known that we, SULLiVAN FENNER and JEROME C. TAFT, both citizensof the United States, and residents of the city and county ofProvidence, in the State of Rhode Island, have invented a new and usefulImprovement in the Manufacture of Twist- Drills, of which the followingis a specification.

In the art of making twist drills as it was known and practiced prior toour invention it had been found that the drills would not clearthemselves easily unless provision was made therefor by a delicate andexpensive I 5 process of grinding or backing 0E of the drill between thegrooves after twisting the blank. So essential to the usefulness andefficiency of the drill was this grinding or backing off considered tobe that inventive 2o skill had been directed to perfecting and producingmachines and devices to perform that duty, and many devices to that endhave been patented. Any process of grinding or backing off a drillinvolves nicety of adjustment and delicacy of manipulation andnecessarily enhances the cost of the manufacture of the drill.

The purpose of our invention is to produce a twist-drill having theproper degree of clearance Without grinding after twisting the blank.lVe accomplish this by forming upon two sides of a drill-blank concavesurfaces for a portion of the length of the blank, and by formingbetween the concave surfaces for a corresponding distance on said blankflat surfaces. In order to insure positively the proper degree ofclearance, weroll or forge one edge of each of the flat surfaces atrifle lower than the other edge. We then twist the blank into spiralform. If, as we consider preferable, we use a blank of about twice thelength of a finished drill, we then cut the blank in two equal lengthsand grind the end of each to a suitable point. The blank,whether ofabout the same or of about twice the length a of the finished drill, isin the first instance of cylindrical form-that is to say, before thegrooves and flat surfaces are rolled therein.

Serial No. 277,465. (No model.)

The finished drill is likewise of cylindrical form.

WVe do not claim herein the rolling of a blank of double the length of afinished drill and then dividing said blank to form two drills at asingle operation, as that process is covered by Letters Patent No.315,530, granted to Samuel Moore, April 14., 1885.

In the accompanying drawings, Figure 1 is an elevation of our completeddrill. Fig. 2 is a plan View of the blank before it is twisted. Fig. 3is an elevation showing the blank twisted to form two drills and showingthe flat surfaces lying between the grooves. Fig. 4 is a section on line00 Q0 of Fig. 2, and Fig. 5 is a cross-section on line w w of Fig. 3.

Similar letters of reference indicate like parts where they occur in thedrawings.

A represents the blank, which has been operated upon by suitablerolls ordies to bring it into the form shown in Fig. 4 in cross-section-that isto say, it is provided with two concave parallel surfaces and with twoparallel flattened faces or edges lying between the concave faces. Wetwist the blank so formed into spiral shape, as shown in Fig. 3, anddivide said blank into two parts to form two drills. It is obvious thatwe can use a blank of sufficient length to form only one drill at asingle operation; but we consider that in rolling drills better resultsare obtainable by the use of the blank of double length.

It is evident that we can form the grooves and flat surfaces by millingor by forging, and in such cases the blank of single length ispreferable.

a a represent the grooves or concave faces, and b b the fiat faces.

B represents a drill constructed according to our invention with theparallel grooved and flattened surfaces.

We claim as our invention and desire to secure by Letters Patent 1. Thedescribed method of manufacturing twist-drills, the same consisting informing on the periphery of the drill between the grooves flat surfaceshaving one edge lower than the other, whereby clearance is afforded tothe drill.

2. As a new article of manufacture, the described drill, provided withfiat surfaces b,1ying parallel with and between the concaved surfaces orgrooves and each having one edge lower than the other to serve, asspecified, to afford clearance to the drill.

In testimony whereof We have hereunto set our hands, in presence of twowitnesses, this IO 24th day of March, 1888.

SULLIVAN FENNER. JEROME C. TAFT.

Witnesses:

HENRY MARSH, J12, MAY D. MASON.

